Silicon and aluminum complexes

ABSTRACT

Silicon and aluminum complexes having the following formula: ##STR1## wherein x is 0 or 1, T is H or ##STR2## each R is independently selected from the group consisting of H, OH, C 1-6  alkyl, C 1-6  alkoxy, C 2-6  alkene, C 6-12  aryl, C 1-6  hydroxyalkyl, C 1-6  thioalkyl, C 2-12  alkoxyalkyl, C 3-20  heteroaromatic, and combinations thereof, wherein R may further contain one or more atoms of a non-carbon element such as Si, Ge, Sn, P, and the like; and Y is a cation, are prepared by reacting silica or alumina with a diol, in the presence of a base, while removing water formed during the reaction. Methods for producing such complexes starting with silica or alumina, and methods for converting such complexes into other silicon or aluminum-containing compounds, are disclosed.

This invention was made in part with Government support under ContractN00014-88K-0305 awarded by the Department of the Navy andF49620-89-C-0059 awarded by the Department of the Air Force. TheGovernment has certain rights in this invention.

FIELD OF THE INVENTION

The present invention relates to complexes containing at least onesilicon or aluminum atom, to the preparation of such complexes startingwith silica or alumina (in various chemical and mineral forms), and tothe use of these complexes to prepare other silicon oraluminum-containing compounds.

BACKGROUND OF THE INVENTION

Silicon-based chemicals are used in a wide variety of applications, suchas in biocides, stain- and dirt-resistant polymers for carpets, advancedceramics for aerospace applications and electronic components. Themarket for silica and other silicon-containing materials amounts toseveral billion dollars per year.

One important aspect of this market, not immediately evident even to afirst-hand observer, is the fact that all silicon-based materials beyondsand are produced by primitive ceramics processing technologies that:(1) add considerable cost to the typical product: (2) limit the scope ofapplications, and (3) offer limited opportunity for growth because ofthe maturity of the process.

Silicon products may be derived from the carbothermal reduction ofsilica to silicon metal: ##STR3## The resulting metallurgical gradesilicon (90-98% purity) must then undergo further processing to makeother products. For example, to make many of the industrially useful(high purity) forms of silica (e.g., fumed or electronics grade silica),it is necessary to first react the Si metal produced in reaction (1)with Cl₂ or HCl to make SiCl₄ which can then be burned (e.g., reaction4):

    Si+2Cl.sub.2 →SiCl.sub.4                            ( 2)

    Si+HCl→HSiCl.sub.3 +SiCl.sub.4                      ( 3)

    SiCl.sub.4 +H.sub.2 O+O.sub.2 →SiO.sub.2 +HCl+HClO.sub.x( 4)

Carbothermal reduction requires high heat and specialized equipment. Theresult is an energy and equipment intensive process. Reaction of siliconwith chlorine or HCl also requires specialized, expensive equipment todeal with toxic and corrosive materials. Despite these considerabledrawbacks, because the basic technology was developed late in the lastcentury and early in this century, all of the processing problems havebeen worked out. This, coupled with economies of scale, makes thisapproach to the production of fumed and electronics grade silicacommercially successful.

Similar problems pervade the alumina and aluminum chemicalstechnologies. Indeed, these technologies are even more expensive andcomplex because of the need to electrolytically reduce moltenalumina/cryolite melts to form aluminum, the source of most aluminumchemicals and many aluminum containing ceramics.

The production of silicon-based chemicals follows somewhat similarchemistry. Most silicone polymers derive from the "Direct Process":##STR4##

This simple reaction only works well when RCl is MeCl or PhCl. When itis MeCl, the major product is Me₂ SiCl₂, which is hydrolyzed andpolymerized to give polydimethylsiloxane, the basic silicone polymer:##STR5##

The above reactions, when coupled with standard organic chemistryreactions, some special derivatives and processing procedures, providethe basis for the major portion of the silicone and silicon chemicalsindustry. It is surprising that there are few, if any, alternate methodsfor producing silicon-based polymers. If there were, and these newmethods provided commercially competitive materials even a fraction assuccessful as the silicone polymers, the rewards would be exceptional.Preferably, these new methods should also involve an inexpensive andreadily available starting material. In view of this, silica is anattractive starting material for producing silicon-containing species,such as those described above.

Silica, SiO₂, is the most common material found in nature. As sand, itis a basic ingredient in building materials, the manufacture of low-techglass products and ceramics. In purer forms, it is used as an abrasive(e.g., toothpaste) and as a drying and texturizing agent in food andfood-related products. It is also used in the manufacture of electronicmaterials and optical products.

Silica is a feedstock material used for the manufacture of silicon-basedchemicals. Synthetic routes stemming from the use of silica gel offerthe important attribute of being very inexpensive (research grade silicasells for ˜$15/kg or less). Additionally, silica gel is very easy tohandle due to its relative nonreactivity. Industrial fused silica sellsfor less than $1/kg, and can be used here.

On the other hand, because of its low reactivity, there are few simple,low-temperature methods of chemically modifying silica. One such methodis dissolution in base to give sodium silicate:

    NaOH+SiO.sub.2 →Na.sub.4 SiO.sub.4                  ( 8)

Unfortunately, this reaction has limited application for the formationof useful feedstock chemicals. The recent work of Kenny and Goodwin[Inorganic and Organometallic Polymers, N. Zeldin et al., ACS SymposiumSeries 360,238, (1987)] on silicic acid esterification provides onesuccessful transformation: ##STR6## Si(OEt)₄, currently produced byreaction of EtOH with SiCl₄, reaction (11), is used commercially to formfumed and electronics grade silica. ##STR7## It is also used to formoptical glasses and boules for spinning fiber optics.

It has been reported that soluble complexes of silicon can be preparedfrom silica gel and catechol in water. These reports teach that thereactions of silica with 1,2 aromatic diols lead to the formation ofhexacoordinate, monomeric silicon complexes: ##STR8## This approach wasmodified and refined by Corriu and co-workers by using basic methanolsolutions under anhydrous conditions. A. Boudin, et. al., Angew. Chem.Int. Ed. Engl, 25 (5):474-475 (1986). These stable salts could then bealklyated by strong nucleophiles, such as Grignard reagents, to formthree (and frequently four) new silicon-carbon bonds: ##STR9##

The problem with this approach is that the catechol complex,tris(1,2-dihydroxobenzoato) siliconate, is relatively expensive and canonly be modified under forcing conditions using expensive reagents suchas LiAlH₄, RMgBr, or RLi and the products are limited to tri ortetrasubstituted silicon. Consequently, its large scale utility islimited. Furthermore, formation of mono-and dialkyl derivatives was notpossible.

The invention described herein resulted from an exploration into methodsof making more reactive complexes of silica using aliphatic 1,2 or 1,3diols, such as ethylene glycol, instead of catechol. Thus, one aspect ofthe present invention described in greater detail hereinbelow, involvescertail novel silicon complexes that may be formed by a reaction betweensilica and 1,2 or 1,3 aliphatic diols. These complexes have beendetermined to contain one or more anionic pentacoordinate silicon atoms.

Previously, pentacoordinate silicon species have been reported. Forexample, U.S. Pat. No. 3,455,980 discloses pentacoordinate siliconcomplexes of vicinal aliphatic diols, including ethylene glycol. Thedisclosure in this patent differs from the present invention, however,in that these prior complexes were not formed from silica but, rather,from a compound of the formula (R'O)₄ Si in the presence of excessaliphatic diol and an amine. Also, the structures of the pentacoordinatesilicon species disclosed in this patent are different from thestructures of those disclosed herein.

U.S. Pat. Nos. 4,632,967, 4,577,003, and 4,447,628 are also directed topentacoordinate silicates, all of which have structures that aredifferent from those of the present invention.

Generally, the prior art has taught that only monomeric, pentacoordinatesilicon complexes derive from monomeric tetracoordinate siliconcomplexes and only dimeric complexes from dimeric starting materials(always bridged by polyalkyl siloxanes). This is despite formingmonomeric pentacoordinate silicon under conditions where sufficient diolis added to form dimeric species.

In an article entitled "Pentacoordinate Silicon Derivatives. IV.¹Alkyl-ammonium Siliconate Salts Derived from Aliphatic 1,2-Diols" [C. L.Frye, J. Am. Chem. Soc. 92:5, 1204-1210 (1970)], there are disclosedsilicon-based compounds that are similar to, but structurally differentfrom, those of the present invention.

Some additional publications that may be relevant to the background ofthe present invention are the following: "Cyclic Pentaoxy Siliconates,"R. R. Holmes et al., Phosphorus Sulfur and Silicon and the RelatedElements 42:1-13 (1989); "Reaction of Grignard Reagents With DianionicHexacoordinated Silicon Complexes: Organosilicon Compounds from SilicaGel," A. Boudin, et. al., Angew. Chem. Int. Ed. Engl, 25 (5):474-475(1986); "Reaction of Catechol with Colloidal Silica and Silicic Acid inAqueous Ammonia," D. W. Barnum, Inorganic Chemistry 11 (6):1424-1429(1972); and "Pentacoordinate Silicon Compounds. V.^(1a) Novel SilatraneChemistry," C. L. Frye, et al., J. Am. Chem. Soc. 93(25):6805-6811(1971).

In spite of previous work involving functionalization of silica andother work involving preparation of pentacoordinate silicon complexes,there has remained a need for new and improved ways of producing usefulsilicon compounds. The present invention provides novel pentacoordinatesilicon complexes, methods of preparing them from silica, and processesfor converting silica into a variety of useful silicon compounds viathese complexes.

In a similar fashion, we find that alumina (Al₂ O₃) can also beconverted to soluble chemical complexes by reaction with base in thepresence of diols.

SUMMARY OF THE INVENTION

An object of the present invention is to enable preparation of usefulsilicon-containing compounds using silica as a starting material.

It is another object of the present invention to obtainsilicon-containing compounds that may be further reacted to produce avariety of useful silicon compounds.

It is yet another object of the present invention to provide a methodfor making soluble silicon products starting with silica and usingsimple and inexpensive reactions.

It is yet another object of the invention to demonstrate that thisapproach can be applied to another metal oxide, alumina.

The above and other objects of the present invention, as willhereinafter become more readily apparent, have been achieved by thediscovery that silica or aluminum can be made to react with aliphaticdiols in the presence of a base and with removal of water during thereaction, to produce pentacoordinate silicon complexes or aluminumcomplexes. These complexes may be relatively easily functionalized byway of further chemical reactions to produce a variety of valuablesilicon and aluminum containing compounds. Through purification andhydrolysis, these compounds can be used directly to form high puritysilica or alumina. Alternatively, when heated they can serve asprecursors to a wide variety of glasses and ceramics.

The initial product of the reaction between the aliphatic glycol andsilica or alumina may also be transformed into other products by way ofligand exchange reactions employing different ligands or cation exchangereactions employing different cations.

In general, the reactions of the present invention to produce silicon oraluminum complexes may be depicted as shown in the following scheme:##STR10## wherein x is 0 or 1, each R is independently selected from H,OH, C₁₋₆ alkyl, O-C₁₋₆ alkyl, C₂₋₆ alkene, C₆₋₁₂ aryl, C₁₋₆hydroxyalkyl, C₁₋₆ thioalkyl, C₂₋₁₂ alkoxyalkyl, C₃₋₂₀ heteroaromatic,and combinations thereof, wherein the R groups may also contain other,non-carbon elements such as Si, Sn, Ge, P, and the like; T is H or##STR11## Y is cationic, most commonly mono or dicationic, but can be acation of higher charge that binds dimers together to form clusters.

The product of the above reaction is a monomeric (T=H) or dimeric(T=other than H) silicon complex or an aluminum complex. As noted above,the product may subsequently be reacted with another ligand or anothercationic species to result in a ligand or cation exchanged product. Theproduct of the above reaction may also be converted into other usefulsilicon or aluminum-containing compounds or ceramics, e.g., via standardmethodologies.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is based on a discovery that silica or alumina canbe converted into silicon or aluminum complexes under relatively mildreaction conditions by causing the silica or alumina to react with analiphatic diol in the presence of a base, while removing water that isformed during the reaction. The reaction produces silicon complexes oraluminum complexes, often in high yield.

The following scheme depicts an exemplary reaction starting with silicato form a complex of the present invention and several secondaryreactions that lead to a variety of useful silicon-containing products:##STR12##

The starting materials, an aliphatic glycol, silica or alumina, and abase, may be obtained from commercial sources, such as the SigmaChemical Company and the Aldrich Chemical Company, or may be synthesizedusing available starting materials and known reactions.

Generally speaking, a molar excess of an aliphatic diol is added tosilica or alumina and a base, a suitable solvent is added, and themixture is allowed to react. It is possible to run the reaction inexcess reactant as solvent. The molar ratio of diol:silica:base istypically 3-5:1-3:1-3 and of diol:alumina:base it is typically3-7:1-3:3-9.

The base used in the reaction is most preferably an alkali metalhydroxide or oxide, such as lithium hydroxide, sodium hydroxide,potassium hydroxide, or cesium hydroxide. The base will generallyprovide the cation, Y, in the final product.

In general, the cation that is present in the final product isrelatively unimportant in the context of the present invention. As faras the inventors are aware, there are no specific requirements to beimposed on the cation, and a chemist will readily be able to select anyof a variety of cations that will work for purposes of the presentinvention. However, many transition metal cations will be reduced ifconditions are not suitable and care in choice of reaction conditionsshould be exercised with this in mind. It is preferred that the cationbe derived from an alkali metal or alkaline earth metal, but it may alsobe derived from other chemical species.

An example of another chemical species that may serve as a cation in thesilicon complexes is a quaternary salt. Suitable quaternary salts havethe general structure:

    R'.sub.4 EX

wherein E is N, P, or Sb; each R' is independently C₁₋₄ alkyl, and X isan anion such as hydroxide or some species that generates OH⁻ onreaction with water.

Exemplary divalent cations are: Mg²⁺, Ca²⁺, Ba²⁺, Ni²⁺, and Co²⁺.

The diol that is employed may be any one having the formula: ##STR13##wherein x is 0 or 1, and each R is independently selected from H, OH,C₁₋₆ alkyl, C₁₋₆ alkoxy, C₂₋₆ alkene, C₆₋₁₂ aryl, C₁₋₆ hydroxyalkyl,C₁₋₆ thioalkyl, C₂₋₁₂ alkoxyalkyl, C₃₋₂₀ heteroaromatic, andcombinations thereof, wherein R may have one or more (preferably 1-3)non-carbon elements, such as Si, Sn, Ge, and P.

The alkyl moieties may be straight chain, branched, and/or cyclic.Exemplary nonlimiting alkyl moieties are: methyl, ethyl, propyl,i-propyl, cyclopentyl, 2-methylbutyl, and the like.

The alkene moieties may be straight chain, branched and/or cyclic.Nonlimiting examples are the mono, di, and polyunsaturated analogues(where possible) of the above-listed alkyl groups having greater thantwo carbon atoms.

The aryl groups are generally aromatic hydrocarbon moieties that have 6to 12 carbon atoms. The aryl groups may be attached directly to the diolor be attached by way of an intervening alkyl moiety. Nonlimitingexamples of the aryl groups are: benzyl, phenyl, and the like.

The hydroxyalkyl groups may be any straight chain, branched, and/orcyclic C₁₋₆ alkyl group substituted with one or more (preferably 1-3)hydroxyl groups. Nonlimiting examples are 1-hydroxyethyl,2-hydroxyethyl, 1-hydroxypropyl, and the like.

The thioalkyl groups may be any straight chain, branched, and/or cyclicC₁₋₆ alkyl attached to the diol by way of a sulfur atom. Nonlimitingexamples are any of the alkyl moieties described above attached by asulfur atom to the diol.

The alkoxyalkyl groups may be any ether moiety containing 2 to 12 carbonatoms. Nonlimiting examples are methoxymethyl, ethoxymethyl,methoxyethyl, and the like.

The heteroaromatic groups may be any C₃₋₂₀ group (preferably C₃₋₈)containing one or more (preferably 1 or 2) heteroatoms (preferably O, N,and/or S). Nonlimiting examples are groups derived from pyridine,thiophene, pyrazine, triazine, etc.

Preferably, the diol is unsubstituted or is independently substituted by1-3 nonhydrogen substituents. Also, the preferred substituents are C₁₋₆alkyl or C₂₋₆ alkenyl. Further, the substituents are preferably locatedon different carbon atoms of the complex.

Some combinations of substituents will not be desirable due toincompatibility, steric crowding, and/or instability under reactionconditions. One of oridinary skill will be able to determine thesecombinations based on standard synthetic considerations and/or routineexperimentation.

Optically active diols are also contemplated; these diols may beresolved before use in the reaction, or may be used as a mixture ofracemates. Similarly, the final products formed by using a diol with anoptically carbon atom may be resolved during purification or may be usedas a mixture of stereoisomers.

Vicinal diols are preferred as the diols herein. However, under somecircumstances, the hydroxyl groups may have a 1, 3 orientation on thediol, depending upon the flexibility of the diol ligand, etc.

Any grade or form of silica may be employed in the reactions. Apreferred silica is 10-400 mesh with minimal organic impurities.However, each beach sand can be used.

Any grade or form of alumina may be used in the reaction. A preferredalumina is 10-400 mesh.

The basic reaction starting with silica or alumina that is describedabove may be conducted in a variety of solvents. Preferred solvents arehigher boiling alcohols such as ethylene glycol, 2-aminoethanol, amylalcohol, 2-ethoxyethanol, and the like. However, other solvents are alsopossible, such as DMSO, sulfolane, N-methyl pyrrolidone.

The reaction will generally be conducted at from ambient temperature tohigher temperatures. Conveniently, the reaction may be conducted at theboiling point of the solvent that is employed. For most purposes, theupper limit of the temperature range will be approximately 200° C.Preferably, the temperature range will be from about 30°-170° C. Mostpreferably, the temperature will range from about 80° C. to 150° C.

It is important that substantially all water that is formed during thereaction be removed as it is formed. It has been found that it the wateris not removed, the products described herein are not obtained, as shownby Example 9, below. Conveniently, the water may be removed byazeotropic distillation; the precise temperature at which water can beazeotropically removed will depend upon the solvents which are used andother conditions, as will be readily understood by a synthetic chemist.The water may also be removed by known water-scavenging species or byany standard membrane transport protocol.

The reaction will typically be carried out for a time period of from afew minutes (e.g., twenty minutes) up to 2-4 days, as necessary.

The final product will often separate out of the reaction mixture as aprecipitate on cooling; however, it may also remain dissolved in thereaction mixture and must be precipitated by addition of a nonsolventsuch as acetonitrile. The product may be isolated and purified by any ofa variety of standard methodologies. For example, the product may betaken up in a solvent, filtered, concentrated, and then crystallized.The crystallized product may then be recrystallized from a suitablesolvent system. In some situations, it may be necessary to carry outcolumn chromatography or another purification procedure to aid in thepurification of the desired product.

In a preferred embodiment, ethylene glycol is reacted with silica in thepresence of an alkali metal hydroxide or oxide to produce a dimericpentacoordinate silicon complex, as depicted below: ##STR14## Otherpreferred reactants, etc., are summarized in the following Table:

    __________________________________________________________________________                            Reaction                                              Diol    Base  Solvent   Temp (°C.)                                                                   Product                                         __________________________________________________________________________    1,2-ethanediol                                                                        MOH   HOCH.sub.2 CH.sub.2 OH                                                                  100-200                                                                             K.sub.2 Si.sub.2 (OCH.sub.2 CH.sub.2                                          O).sub.5                                                M = Li,                                                                       Na, K, Cs                                                             1,2-ethanediol                                                                        M(OH).sub.2                                                                         HOCH.sub.2 CH.sub.2 OH                                                                  100-200                                                                             MSi.sub.2 (OCH.sub.2 CH.sub.2 O).sub.5                  M = Mg,                                                                       Ca, Sr, Ba                                                            1,2-ethanediol                                                                        Ca(OH).sub.2                                                                        H.sub.2 NCH.sub.2 CH.sub.2 OH                                                           100-200                                                                             CaSi.sub.2 (OCH.sub.2 CH.sub.2 O).sub.5         1,2-ethanediol                                                                        Ca(OH).sub.2                                                                        HSCH.sub.2 CH.sub.2 OH                                                                  100-200                                                                             CaSi.sub.2 (OCH.sub.2 CH.sub.2 O).sub.5         1,2-ethanediol                                                                        Ca(OH).sub.2                                                                        Eu--OCH.sub.2 CH.sub.2 OH                                                               100-200                                                                             CaSi.sub.2 (OCH.sub.2 CH.sub.2 O).sub.5         1,2-ethanediol                                                                        Ca(OH).sub.2                                                                        H(OCH.sub.2 CH.sub.2).sub.2 OH                                                          100-200                                                                             CaSi.sub.2 (OCH.sub.2 CH.sub.2 O).sub.5         1,2-ethanediol                                                                        Ca(OH).sub.2                                                                        HN(CH.sub.2 CH.sub.2 OH).sub.2                                                          100-200                                                                             CaSi.sub.2 (OCH.sub.2 CH.sub.2 O).sub.5         1,2-ethanediol                                                                        Ca(OH).sub.2                                                                        O(CH.sub.2 CH.sub.2 OH).sub.2                                                           100-200                                                                             CaSi.sub.2 (OCH.sub.2 CH.sub.2 O).sub.5         Pinacol MOH   HOCH.sub.2 CH.sub. 2 OH                                                                 100-200                                                                             M.sub.2 Si.sub.2 (OCMe.sub.2 CMe.sub.2                                        O).sub.5                                                M = Li,                                                                       Na, K, Cs                                                             Glycerol                                                                              MOH   HOCH.sub.2 CH.sub.2 OH                                                                  100-200                                                                             M.sub.2 Si.sub.2 (OCH.sub.2 CH(CH.sub.2                                       OH)O).sub.5                                             M = Li,                                                                       Na, K, Cs                                                             1,2-propanediol                                                                       MOH   HOCH.sub.2 CH.sub.2 OH                                                                  100-200                                                                             M.sub.2 Si.sub.2 (OCH.sub.2 CH(CH.sub.3)O).s                                  ub.5                                                    M = Li,                                                                       Na, K, Cs                                                             1,3-propanediol                                                                       MOH   HOCH.sub.2 CH.sub.2 OH                                                                  100-200                                                                             M.sub.2 Si.sub.2 (OCH.sub.2 CH.sub.2                                          CH.sub.2 O).sub.5                                       M = Li,                                                                       Na, K, Cs                                                             1-amino-2,3                                                                           MOH   HOCH.sub.2 CH.sub.2 OH                                                                  100-200                                                                             M.sub.2 Si.sub.2 (OCH.sub.2 CH(CH.sub.2                                       NH.sub.2)O).sub.5                               propanediol                                                                           M = Li,                                                                       Na, K, Cs                                                             cyclohexane                                                                           Ca(OH).sub.2                                                                        HOCH.sub.2 CH.sub.2 OH                                                                  100-200                                                                             CaSi.sub.2 [1,2-(O).sub.2 Cyc].sub.5            (Cyc) 1,2-diol                                                                1,2-diphenyl-                                                                         Ca(OH).sub.2                                                                        HOCH.sub.2 CH.sub.2 OH                                                                  100-200                                                                             CaSi.sub.2 [1,2-(O).sub.2 Dip].sub.5            ethane                                                                        1,2-diol (dip)                                                                __________________________________________________________________________

Additional details on the basic reaction parameters as applied tospecific reactants are provided in the Examples section hereinbelow.

After the product is formed in the above reaction, it may either bepurified as described above or may be converted in situ into otherproducts, as desired. The silicon or aluminum complexes may be treatedwith a variety of reactants, including HCl, acetic anhydride, acetylchloride, additional silica or alumina, and the like. These treatmentswill produce, in a staightforward manner, various functionalizedaluminum- or silicon-containing species. Examples of silicon speciesthat may be obtained in this manner are: Si(OCH₂ CH₂ O)₂, SiCl₄,Si(OAC)₄, SiC (produced by heating), crystalline silicon containingspecies (e.g., quartz), zeolitic-like products, neutralsilicon-containing polymers, and the like. Examples of aluminum speciesare alkaline earth aluminate glasses and ceramics, etc.

The ionic polymers produced by exchange, e.g., Example 6, can be used ascoatable ion conductors for making clear electrodes for electronicdisplays, nonlinear optical applications and for battery applications.

In addition to the above-described reactions starting with the siliconand aluminum complexes, exchange reactions may also be carried out. In aligand exchange reaction, the complex is treated with an excess amountof a ligand that is different from the diol used to form the complex.During the reaction, the new ligand will take the place of theoriginally used diol in the complex.

Alternatively or concurrently, the silicon or aluminum complex may besubjected to a cation exchange reaction by contacting the complex withan excess amount of a cationic species that is different from thestarting cationic species. For example, if potassium hydroxide were usedin the initial reaction, producing a potassium salt of a pentacoordinatesilicon complex, an exchange reaction with an ammonium salt could beused to substitute an ammonium cation for the potassium cation. However,care should be taken in carrying out such a reaction to avoidconditions, particularly acid conditions, in which the cyclic dioxymoiety in the complex is cleaved. Examples of exchange reactions arealso described in the Examples section below.

Analogous processes and approaches can be used when Al₂ O₃ rather thansilica is used as the metal oxide reactant.

The invention now being generally described, the same will be betterunderstood by reference to certain specific examples which are includedherein for illustrative purposes only, and are not intended to belimiting of the present invention.

EXAMPLES A. General 1. Procedures

All operations were carried out with the careful exclusion of extraneousmoisture. Air-sensitive materials were manipulated using standardSchlenk and glovebox techniques. ¹ H, ¹³ C and ²⁹ Si spectra NMR spectrawere taken in CD₃ OD and referenced to TMS. All chemicals were purchasedfrom standard vendors and used as received, except the diols, which weredistilled under nitrogen before use.

2. Equipment

Infrared spectra were recorded on an IBM FTIR-44 spectrophotometer.Nuclear magnetic resonance data were collected on a Varian 300 MHzspectrometer. Elemental analyses were performed by GalbraithLaboratories in Knoxville, Tenn.

B. Materials 1. Preparation of K₂ Si₂ (OCH₂ CH₂ O)₅

13.8 grams of 400 mesh silica gel (0.23 mol) and 14.8 grams (0.26 mol)of potassium hydroxide (85%) were weighed into a 500 mL round bottomflask. 125 mL of freshly distilled (from Mg/MgI₂) EtOH and 250 mL ofdistilled ethylene glycol were added to the flask and the mixture washeated to boiling. The ethanol fraction was distilled off to remove (byazeotrope) any water formed during the reaction. The mixture was thenheated further until the solution appeared homogeneous. Partialdissolution of the silica occurred during this period. Distillation wascontinued to remove the major fraction of the excess ethylene glycol andwater formed during reaction. During distillation, most of the silicadissolved. Upon cooling, the remaining colorless liquid turned to asticky white solid mass. This mass was taken up in 350 mL of freshlydistilled methanol and filtered through a Celite-covered frit. Thefiltrate was concentrated in vacuo to ˜20 mL after which portions of dryacetonitrile were added slowly to precipitate out a fine white powder.The precipitate was then collected on a glass frit and washed with 3×200mL of acetonitrile. Recrystallization from methanol andacetonitrile/ether resulted in a pure white powder which wasvacuum-dried. This resulted in 90 g (0.21 mol) of product or 90% yield.NMR: ¹ H, 3.4 ppm (under solvent peak); ¹³ C, 61.1, 64.3 ppm; ²⁹ Si,-103.0 ppm. Elemental analysis, calc. (found) % C, 27.53 (27.63); % H,4.98 (4.64); % Si, 13.60 (12.92); % K 17.84 (17.99); % O by difference,37.01 (36.81).

2. Production of Functionalized Silicon-Containing Species

When K₂ Si₂ (OCH₂ CH₂ O)₅ is added slowly to neat anhydride and heated,initially, KOAc can be filtered off after the reaction is cooled. Acetylchloride can also be used. Removal of excess anhydride and1,2-ethanediacetate under vacuum leads to a white solid which can becharacterized as Si(O₂ CCH₃)₄.

Treatment with two equivalents of HCl, followed by filtration of the KClleads to the isolation of a neutral tetracoordinate, polymeric siliconcompound with the empirical formula Si(OCH₂ CH₂ O)₂, which is inequilibrium with the excess ethylene glycol formed during neutralizationto form ring opened diols, e.g., Si(OCH₂ CH₂ O)₂ (OCH₂ CH₂ OH)₂, thatcan be used in place of Si(OEt)₄ for sol-gel processing of silicacontaining glasses. At higher concentrations, the Si(OCH₂ CH₂ O)₂ (OCH₂CH₂ OH)₂ species are in equilibrium with oligomeric/polymeric formswhose rheology can be controlled by removal of excess ethylene glycol orsolvent addition to form coatable or spinnable materials that can serveas precursors to silicon-containing ceramics. These neutral fourcoordinate silicon-containing species can be used as precursors to othersilicon containing species using techniques common to the polysiloxanesynthetic chemist.

3. Preparation of Li₂ Si₂ (OCH₂ CH₂ O)₅

A procedure similar to that used for the potassium derivative wasemployed using 5.00 g (0.083 mol) of silica and 1.98 g (0.083 mol) ofLiOH. When the "polymeric" portion of the product, that portion which isnot immediately soluble, was left stirring for 1-2 days in methanol, itdissolved quantitatively. The resulting methanol-soluble material wasrecrystallized from methanol and acetonitrile/ether and vacuum-dried.This resulted in 26.2 g (71 mmol) of product or 85% yield. ¹³ C, 61.2,64.4 ppm; ²⁹ Si, -102.9 ppm.

4. Preparation of Na₂ Si₂ (OCH₂ CH₂ O)₅

Procedures identical to those described for the preparation of thepotassium salt were used except 3.33 g (83 mmol) of NaOH were used.Again, stirring for 1-2 days in methanol resulted in completedissolution. The methanol-soluble material could be recrystallized asabove and dried in vacuum. This resulted in 26 g (75 mmol) of product or90% yield. NMR (CD₃ OD): ¹ H, 3.36 ppm; ¹³ C, 63.2 ppm; ²⁹ Si, -103.3ppm.

5. Preparation of CsSi(OCH₂ CH₂ O)₂ (OCH₂ CH₂ OH)

Procedures identical to those described for the preparation of thepotassium salt were used except 8.74 g (83 mmol) of CsOH were used. Theproduct in this instance was entirely soluble in ethanol. The productwas precipitated out by addition of acetonitrile. Although almost all ofthe silica dissolved, the isolated yield was only 53%. NMR (CD₃ OD): ¹H, 3.4 ppm (under solvent peak); ¹³ C, 63.2 ppm; ²⁹ Si, -103.1 ppm.Elemental analysis, calc. (found) % C, 20.72 (21.06); % H, 3.63 (3.83);% Si, 8.58 (8.21); % Cs 39.38 (38.84); % O by difference, 27.32 (27.06).IR (nujol) υ O--H=3300.

6. Exchange of Pinacol for Ethylene Glycol

1.5 g (3.46 mmol) of K₂ Si₂ (OCH₂ CH₂ O)₅ were mixed with 80 mL offreshly distilled pinacol (added as a solvent). The reaction mixture wasthen heated under N₂. The mixture melted, the siliconate dissolved andheating was continued until 65 mL of a mixture of ethylene glycol andpinacol were distilled off. On cooling, the remaining liquid became awhite solid. Excess pinacol was washed away using 2×50 mL ofacetonitrile. The remaining white material was then dissolved inmethanol and recrystallized as above. The yield was essentiallyquantitative. The product is expected to be K₂ Si₂ (OCMe₂ CMe₂ O)₅. NMR(CD₃ OD): ¹ H, 3.4 ppm (under solvent peak); ¹³ C, 75.8, 26.5, 25.9 ppm;²⁹ Si, -109 ppm.

7. Exchange of 1,3-Propanediol for Ethylene Glycol

5.0 g (11.5 mol) of K₂ Si₂ (OCH₂ CH₂ O)₅ were mixed with 50 mL offreshly distilled 1,3-propanediol (added as a solvent). The reactionmixture was then heated under N₂. The siliconate dissolved and heatingwas continued until a 35 mL mixture of ethylene glycol and propanediolwas distilled off. The remaining solution was syringed into 50 mL ofcold diethyl ether. The product collected as an oil at the bottom of theflask. The oil was cannulated into a 50 mL Schlenk flask and dried invacuo to a clear glassy solid. This solid was dissolved in 15 mL of MeOHand syringed into 70 mL of acetonitrile to give a precipitate which wasfiltered off on a medium frit. NMR (CD₃ OD): ¹ H 1.75 quintet, 1.74quintet, 3.35 s, 3.66 triplet, 3.67 triplet, 5.13 s ppm; ¹³ C, 60.0 and36.3 ppm; ²⁹ Si, -107.2 ppm. The product can be partially polymeric.

8. Exchange of PEG₄ for Ethylene Glycol

5.0 g (13.5 mmol) of Li₂ Si₂ (OCH₂ CH₂ O)₅ were mixed with 50 mL ofethylene glycol. The stirred solution was heated under N₂ until all ofthe lithium salt dissolved. 40 mL freshly distilled PEG₄ (tetraethyleneglycol) were then added. The execess ethylene glycol was distilled offto give a clear yellow solution. 20 mL of PEG₄ were removed bydistillation at reduced pressure. 40 mL of EtOH were then added andacetonitrile was added to precipitate a crude glassy polymeric productwhich was filtered and dried in vacuo. The crude material wascharacterized by ¹³ C NMR (CD₃ OD): ¹³ C, 73.6, 71.3, 64.3 and 62.1. Thelatter two peaks may indicate some ethylene glycol remains. Thestructure may be polymeric.

9. Attempt to Synthesize Ba[Si₂ (OCH₂ CH₂ O)₅ ]

The following reaction was attempted: ##STR15##

6.38 g (4.16 10⁻² mol) of BaO were dissolved in 250 ml of EtOH, at roomtemperature, in a 500 ml Schlenk flask. Then 5.00 g (8.32 10⁻² mol) of400 mesh SiO₂ 11.6 ml (d=1.114 g/ml; 0.208 mol) of ethylene glycol wereadded to the solution.

Approximately 150 ml of ethanol were distilled out to form Ba(OCH₂ CH₂O), then 100 ml of ethanol were added, and the suspension was allowed toreflux for 16 hours. Most of the ethanol was then distilled out, leavinga white, viscous suspension. The rest of the solvent was removed undervacuum. The white residue was treated with 250 ml of methanol, and thesystem was allowed to stir for one hour; part of the initial residueproved to be insoluble. This latter was collected by filtration througha fritted filter, washed with methanol and vaccum dried. It resulted inessentially quantitative recovery (4.9 g) of unreacted silica. Thesolvent from the methanolic solution was removed under vacuum, leaving avery thick liquid as residue. This latter was dissolved in the minimalamount of ethanol (˜20 ml) and treated with 60 ml of acetonitrile: awhite fine product precipitated out (8.99 g). The amount of recoveredproduct is in accordance with the formation of [Ba(OCH₂ CH₂ O)]. The ¹ Hand ¹³ C nmr spectra (CD₃ OD) show the following peaks: ¹ H nmr; 3.62ppm; 5.35 ppm; ¹³ C nmr: 64.80 ppm.

10. Synthesis of the Aluminum Glycolate

5 g (0.049 mol) of Al₂ O₃ and 7.03 g (0.294 mol) of lithium hydroxidewere weighed in a 500 ml round bottom flask. Then 250 ml of ethyleneglycol and 60 ml of ethanol were added. The mixture was allowed to heat,and first the ethanol/water azeotrope was distilled off. Then most ofthe ethylene glycol was removed by distillation. The system was cooledand left under nitrogen overnight; after 12 hours there was a whitesolid mass, which was treated with methanol; and solid went almostentirely in solution (there was only a slight cloudiness, which waseliminated by filtration through celite). The volume of the solution wasreduced under vacuum until a white solid started to percipitate out; theprecipitation was completed by adding acetonitrile, and then the productwas filtered and dried under vacuum. The yield was quantitative. NMR(CD₃ OD): ¹ H, 3.58 ppm and 5.11 ppm; ¹³ C, 64.32 ppm.

The invention now being fully described, it will be apparent to one ofordinary skill in the art that many changes and modifications can bemade thereto, without departing from the spirit or scope of theinvention as set forth herein.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A complex having theformula ##STR16## wherein x is 0 or 1; each R is independently selectedfrom the group consisting of H, OH, C₁₋₆ alkyl, C₁₋₆ alkoxyl, C₂₋₆alkene, C₆₋₁₂ aryl, C₁₋₆ hydroxyalkyl, C₁₋₆ thioalkyl, C₂₋₁₂alkoxyalkyl, C₃₋₂₀ heteroaromatic, and combinations thereof, and whereineach said R group may further contain one or more atoms of elementsselected from the group consisting of Si, Ge, Sn and P;T is H or##STR17## and Y is an alkali metal cation.
 2. A complex according toclaim 1, wherein each R is independently a methyl group or H.
 3. Acomplex according to claim 1, wherein every R is H.
 4. A complexaccording to claim 1, wherein T is ##STR18##
 5. A silicon complexaccording to claim 1, wherein Y is Cs⁺ and T is H.
 6. A silicon complexaccording to claim 1, wherein Y is 2Na⁺, 2Li⁺, or 2K⁺ and T is ##STR19##7. A silicon complex selected from the group consisting of K₂ Si₂ (OCH₂CH₂ O)₅, Li₂ Si₂ (OCH₂ CH₂ O)₅, and Na₂ Si₂ (OCH₂ CH₂ O)₅ [, BaSi₂ (OCH₂CH₂ O)₅, and CaSi₂ (OCH₂ CH₂ O)₅ ].